I. Field of the Invention
The present invention relates generally to wireless communication systems. More particularly, the present invention relates to a novel and improved system and method of power control for a wireless communication device.
II. Field of the Invention
Wireless communication networks are enjoying notable popularity in all aspects of business, industry and personal life. As such, portable, hand-held wireless communication devices have experienced widespread growth in recent years. Portable devices such as cellular and Personal Communication Services (PCS) phones are now commonplace for business and personal users alike. Additionally, advanced systems, such as satellite communications systems using portable, hand held and mobile phones, are on the horizon.
One design goal of hand-held communication devices is that of low power consumption. Low power consumption provides lower heat generation and extended battery life which increases device usefulness. Often times, lower power consumption also allows for or leads to smaller device sizes.
In CDMA communication systems, the transmitted power of signals within the system is controlled so as to maintain the amount of power required for any given communication link at a minimum level. This serves to maximize overall communication system capacity and maintain acceptable levels of mutual interference and signal quality. By controlling the transmitted signal power at or near the minimum level, interference with other communication devices or units is reduced. Examples of techniques for power control in such communication systems are found in U.S. Pat. Nos. 5,383,219, entitled "Fast Forward Link Power Control In A Code Division Multiple Access System," issued Jan. 17, 1995; 5,396,516, entitled "Method And System For The Dynamic Modification Of Control Parameters In A Transmitter Power Control System," issued Mar. 7, 1995; and 5,267,262, entitled "Transmitter Power Control System," issued Nov. 30, 1993, which are incorporated herein by reference.
One technique for decreasing the amount of power consumed by the device is to minimize the amount of power in the transmitted signal. Often times, this is accomplished by decreasing the amount of power in the transmitted signal as much as possible without the signal-to-noise ratio (SNR) falling below an acceptable level. When the SNR falls below the acceptable level, the power is increased to bring the SNR back up to an acceptable level.
This approach is advantageous because it allows a minimum amount of power to be used for communications under optimum conditions. When operating in less than optimum or ideal conditions that is, inside a building, in bad weather, or such, transmission power is increased to maintain acceptable SNR and communications quality.
With some systems, such as cellular or other wireless communications systems for example, the wireless communication device, that is, a cellular phone, is controlled remotely. That is, part of the communication bandwidth between the device and a base station transceiver is dedicated to transferring command and status information. This command and status portion of the bandwidth is used to adjust the power of signals transmitted by the device. When the SNR of communication signals received by a base station falls below an acceptable level, the base station sends a command to the wireless device to increase its transmitted power. Similarly, if the SNR of the received communication signals is well within acceptable limits, the base station commands the device to decrease transmitter power.